DISEASE CHARACTERISTICS:

• Histologically confirmed metastatic breast cancer that expresses carcinoembryonic antigen (CEA)

  • At least 25% of the tumor cells must stain positive for CEA with at least moderate intensity
• Must have achieved either partial response or complete response after high dose chemotherapy and peripheral blood stem cell transplant

• Hormone receptor status:

  • Not specified

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Menopausal status:

• Not specified

Performance status:

• Karnofsky 70-100%

Life expectancy:

• Greater than 6 months

Hematopoietic:

• Absolute neutrophil count at least 1000/mm^3
• Absolute lymphocyte count at least 1000/mm^3
• Hemoglobin at least 9 mg/dL
• Platelet count at least 100,000/mm^3

Hepatic:

• Bilirubin less than 2.0 mg/dL
• No serious ongoing chronic or acute hepatic disease

Renal:

• Creatinine less than 2.5 mg/dL

Cardiovascular:

• No serious ongoing chronic or acute cardiac disease (New York Heart Association class III or IV)

Pulmonary:

• No serious ongoing chronic or acute pulmonary illness such as asthma, chronic obstructive pulmonary disease, or radiation or drug induced pneumonitis

Other:

• No other prior or concurrent malignancy except nonmelanoma skin cancer or controlled superficial bladder cancer within the past 5 years
• No history of autoimmune disease such as inflammatory bowel disease, systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis, scleroderma, or multiple sclerosis
• No inflammatory bowel condition such as active infectious enteritis or eosinophilic enteritis
• No active acute or chronic infection such as urinary tract infection, HIV, or viral hepatitis
• Not pregnant or nursing

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• See Disease Characteristics
• No concurrent immunotherapy

Chemotherapy:

• See Disease Characteristics
• No concurrent chemotherapy

Endocrine therapy:

• At least 4 weeks since steroids
• No concurrent steroid therapy

Radiotherapy:

• No concurrent radiotherapy

Surgery:

• Not specified

Other:

• No concurrent immunosuppressive agents such as azathioprine or cyclosporine A